Titanium dioxide, which is n-type semiconductor, has been known as a photocatalyst that activates various chemical reactions with ultraviolet radiation energy, such as chemical reactions resulted in during a process of pasteurization and decomposition of organic substance. On the other hand, various methods to carry a photocatalyst layer onto a glass plate, plastics, tiles, etc. have been proposed (See JP Laid-opened No. Sho 62-66861 and No. Hei 5-309267, EP 633064 and U.S. Pat. No. 4,888,101) have been proposed. However, these methods are respectively having problems, such as insufficient photocatalytic activity and short durability.
In WO 97-134 gazette, an example which enables to provide a resin structure having high photocatalytic activity and excellent durability prepared by means of carrying a photocatalyst layer composed of photocatalyst particles complex containing metal oxide gel thereon via an adhesive layer composed of acrylsilicon resin added with polysiloxane by either dipping or spraying method is disclosed. For carrying a photocatalyst onto a metallic plate, a coated metallic plate, a resin-coated metallic plate, an enamelled metallic plate, a resin substrate or a coated resin substrate for aiming at providing antifouling, antibacterial and deodorant activity, a method to directly provide a photocatalyst structure which is supporting a photocatalyst layer via an adhesive layer onto a metallic plate or the like can be employed. However, such method has problems in production cost, since it requires long drying process after coating, and particularly in case of a metallic plate or a resin substrate longer than one meter, a big size drier and long drying process more than 30 minutes are required, which is the cause to make production speed slow and high cost. In addition, there are further problems in the process in large scale production point of view such that the type and the size of applicable metallic plates and resin structures might be limited because of the reasons that a metallic plate or a resin structure can be corroded to cause aerugo at the time of coating and drying process depending upon pH in the coating solution to be coated onto a adhesive layer and photocatalyst layer, and coating to form a uniform layer onto a metallic plate or a resin structure either by dipping or spraying can be difficult in case of forming a thick layer more than 1 mm and then to cause the thickness of a layer irregular.
On the other hand, the difficulty mentioned above can be resolved if it is possible to laminate a film, which is uniformly coated with a transparent photocatalyst layer in advance onto a metallic plate or a resin substrate, even though taking the time required for laminating the film onto a flat layer into consideration, because efficiency to produce films for lamination use is higher than the coating the solution onto such structures. In WO 97-134 gazette, a laminating film prepared by coating a sticking agent onto a reverse side of a photocatalyst-supporting film is disclosed. However, for industrial scale production, laminating a film by means of heating and pressing requires less production process than laminating by means of adhesion. Further, for molding laminated-products, laminated films by means of heating and pressing is more advantageous from a view point that those films can be molded and processed without considering shrinkage of an adhesive layer by heating. However, due to laminating by heating and pressing, the activity of a photocatalyst may deteriorate. Therefore, no resin structure whereto a photocatalyst-supporting film is laminated by heating without getting reduction of photocatalytic activity onto a metallic plate or a resin structure, particularly onto a polycarbonate resin and poly(vinyl chloride) resin reinforced with a cloth being widely-used, has known.
Moreover, the coating solution disclosed in the gazette has difficulty in sufficient drying and hardening of the solution at forming films at high speed, thereby causing a problem of adhesion of the coated-solution to the reverse side of the film. Particularly, films which can be laminated by heating and pressing normally have low heat-resisting property and low distortion temperature such like 100° C. or lower, it is difficult to use the coating solution and the coating process disclosed in WO 97-134 gazette for high speed lamination of films suitably laminated by heating.